Articles of incorporation is the founding legal document a company's organizers file with a state government to formally bring a corporation into existence as a separate legal entity. Among the details it typically sets out are the corporation's official name, its registered address, its stated business purpose, and critically for accounting purposes, the number of shares of stock it is authorized to issue.
What the document actually establishes
Once accepted and filed by the relevant state authority, articles of incorporation create a legal entity distinct from its owners, which is the foundation for the limited liability protection shareholders in a corporation enjoy. The document also typically names the corporation's initial directors or incorporators, and may set out basic governance provisions, though most of the detailed internal rules a corporation actually operates under are set separately in its bylaws, a document the board can generally amend more easily than the articles themselves.
The number and classes of shares stated in the articles of incorporation set a ceiling on how much capital stock the corporation can issue without amending the document and refiling with the state. This authorized share count is distinct from the number of shares actually issued and outstanding at any given time, which is almost always lower, and from treasury shares, which have been issued and later repurchased. A corporation that wants to issue more shares than its articles currently authorize must formally amend the articles first, typically requiring shareholder approval.
Amendments and ongoing relevance
Articles of incorporation are not static; corporations routinely amend them over time to increase authorized shares ahead of a stock split or new financing round, change the corporate name, or adjust other foundational provisions, with each amendment filed and recorded by the state the same way the original articles were. Because of this, a corporation's capitalization history can often be traced directly through its sequence of amended and restated articles of incorporation.
Why the document matters to outside parties
Lenders, investors, and auditors reviewing a company's capital structure routinely check its articles of incorporation to confirm the corporation's authorized share count has not been exceeded and that any newly issued stock, convertible securities, or stock options remain within the limits the articles permit. A corporation that issues shares beyond what its articles currently authorize has created a legal defect in that stock issuance, which is exactly the kind of structural problem a careful review of the articles is meant to catch before it becomes a dispute.
A simple worked example
A startup's original articles of incorporation might authorize 10 million shares of common stock. After issuing 6 million shares to founders and early investors, the company still has 4 million authorized but unissued shares available to grant as employee stock options or sell in a future financing round, without needing to amend its articles — but once it has issued or committed close to the full 10 million, it must amend the articles and refile with the state before it can authorize any more.